Homogenization is an industrial process which has been used for a considerable length of time, and its purpose is, in a fat emulsion such as, for example, milk, to split the largest fat globules into smaller fat globules and by such means stabilize the fat emulsion. For, for example milk, this implies that cream setting is prevented, and the vast majority of all consumer milk today is homogenized.
Homogenization normally takes place by mechanical processing, so that the fat emulsion which has a high input pressure is forced at high speed to pass through a very narrow gap, where the fat globules of the fat emulsion are broken up as a result of the turbulence which occurs at great speeds and through cavitation bubbles which implode in the liquid. The process takes place during an extremely short period of time and what happens during this period of time is that the speed of the fat emulsion on passage increases while the pressure decreases, with the result that the liquid begins to boil.
A homogenizer consists essentially of a large piston pump which delivers a high pressure, as well as a counter-pressure device where the homogenization proper takes place. The counter-pressure device, or homogenizer valve, in turn consists of a pressurized, resilient valve cone, a valve seat as well as a wear ring or gasket and a valve housing surrounding the valve cone and valve seat. The valve cone and valve seat are normally rotation-symmetrical and are disposed such that there occurs between these two parts a radial throttle, which constitutes a homogenization gap. The height, width and length of the gap determine that volume at which the homogenization takes place. This volume must be sufficiently small to obtain an efficient homogenization. The gap height is reduced at a higher pressure on the liquid which is to be homogenized, at the same time as a larger flow entails that the gap height is increased.
Above all in the homogenization of pasteurized milk, compared with UHT treated milk (Ultra High Temperature), use is made of a lower pressure at the same time as the intention is to increase the flow quantity. This implies that the homogenizer valve would need to be made larger, so that the gap height is reduced, in order to obtain a good level of homogenization at this lower pressure and increased flow. However, it has proved that an up-scaling of existing, well functioning homogenizer valves not always functions satisfactorily in practice. The larger the pressurized surface, the greater the forces will be that arise and the larger the homogenizer valve. Simultaneously, the costs for such a homogenizer valve increase by several factors.
Another method of solving problem is to connect in parallel a number of homogenizer gaps, as shown in European Patent Specification EP 034 675. By such means, there will be obtained an extension of the gap length and thereby a reduction of the gap height. This type of homogenizer valve with homogenization gaps connected in parallel has, however, an as good as fixed gap height. It permits only one flow and one homogenization pressure without retro-structuring. It also suffers from the drawback of wear in an uneven and uncontrollable manner, which harmfully affects the homogenization result.
Swedish Patent Specification SE 509 103 discloses yet a further solution to how the gap length can be extended by up to three times. This takes place by designing the valve seat and the valve cone so that a plurality of concentric homogenization gaps occurs. This homogenizer valve may be regulated for different flows.